1. Field of the Invention
The present invention relates generally to a portable wireless apparatus, and more particularly, to a portable wireless apparatus in which a leakage current generated in a circuit ground plate included in a circuit substrate is reduced.
2. Description of the Related Art
In a portable wireless apparatus such as a Personal Data Assistant (PDA) and a notebook computer, a circuit including a base band circuit generates noise due to a high frequency characteristic of a wireless part. In order to prevent noise, a wireless part substrate including an antenna and a circuit substrate are conventionally separated from each other.
However, the antenna and the circuit substrate are partly electrically connected by a feeder. Thus, a leakage current from the antenna flows to the circuit substrate and a circuit ground plate included in the circuit substrate. A large circuit substrate greatly affects antenna radiation patterns and a communication band. For example, in the conventional portable wireless apparatus including a large circuit ground plate, antenna radiation patterns have a peak toward the circuit ground plate, which is not preferable for radio communication.
In addition, in the portable wireless apparatus, a current distribution of a current flowing in the circuit substrate is affected by the position of the hand of a user, for example, which influences the characteristics of the portable wireless apparatus.
Japanese Patent Laid-Open Publication No. 2003-198409 discloses a device for reducing the influence of the leakage current of the antenna. According to the disclosed device, the leakage current is reduced by separating a wireless part substrate from a control substrate in a parallel direction to both substrates and specifying a position of a connector. However, the device has a complicated structure and is not suitable for an antenna array or a similar structure.